The broad objective of this research is to determine the biological functions of Z-disk proteins, especially alpha-actinin, in striated muscle and other nonmuscle movement systems. The specific objectives are: 1) to specify the nature of the proteins constituting Z-disks in striated muscle or Z-disk analogues in nonmuscle systems; these efforts will use selective extraction, biochemical characterization, and localization of antibody binding with the light and electron microscope; 2) to determine whether alpha-actinin or other Z-disk proteins can modify actin structure in a way that alters the ability of actin to function in biological movement; these experiments will involve assays of the effects of alpha-actinin or other Z-disk proteins on the conformation of actin monomers while these monomers are aggregated in filaments; 3) to ascertain the role of Z-disk proteins in disassembly of contractile systems during metabolic turnover and to learn the mechanism of this disassembly; these experiments will involve studies of the endogenous Ca 2 ions-activated protease that degrades Z-disks and characterization of this protease and other muscle proteases that may be involved in myofibrillar protein turnover. BIBLIOGRAPHIC REFERENCES: Harbison, S.A., Goll, D.E., Parrish, F.C., Jr., Wang, V., and Kline, E.A. (1976). Muscle growth in two genetically different lines of swine. Growth 40, 253-283. Dayton, W.R., Goll, D.E., Zeece, M.G., Robson, R.M., and Reville, W.J. (1976). A Ca 2 ions-activated protease possibly involved in myofibrillar protein turnover. Purification from porcine muscle. Biochemistry 15, 2150-2158.